1. Field
Example embodiments relate to methods for operating an image sensor. More particularly, example embodiments relate to an image sensor that may reduce and/or prevent the occurrence of blooming phenomenon.
2. Description of the Related Art
An image sensor transforms photonic images into electrical signals. Recent advances in computer and communication industries have led to strong demands in high performance image sensors in various consumer electronic devices including digital cameras, camcorders, PCSs (Personal Communication Systems), game devices, security cameras, and medical micro cameras.
Specifically, a CMOS image sensor has simple operating methods and may be implemented using various scanning methods. The size of a product may be minimized since signal processing circuits may be integrated into a single chip. Additionally, the fabricating cost may be reduced since MOS process technologies may be reused. Also, CMOS image sensors may require relatively small power consumption, which may be useful in battery-powered applications. The use of CMOS image sensors has been rapidly increasing as a result of these advances in implementation of high resolution CMOS image sensors.
Conventional image sensors may be formed from multiple active pixels. Each unit pixel may include a photoelectric conversion unit that responds to incident light and generates charges. Each unit pixel may also include a charge transmission unit that transfers charges generated to a charge read unit.
However, in conventional image sensors, a relatively high illumination may charge a unit pixel's photodiode to beyond capacity, which may lead to blooming phenomenon, where charges overflow into neighboring photodiodes.
Conventional methods to prevent blooming may include installing an overflow drain which is adjacent to a photoelectric conversion unit or installing a separate gate. However, these methods may not completely prevent blooming and may decrease sensitivity.